More and more services are carried in the wireless network with development and evolution of a wireless network, and therefore, extra spectrum resources are required to support a large amount of data transmission. The spectrum resources may be characterized by for example parameters such as time, frequency, bandwidth, maximum allowable emission power and so on. Limited spectrum resources have been allocated to fixed operators and services. New available spectrum is very rare or expensive. In this case, a concept of dynamic spectrum usage is proposed, that is, spectrum resources which have been allocated to some systems or services but are not used sufficiently are used dynamically. The spectrum resources are unlicensed for a system which uses the spectrum resources dynamically. A wireless communication system determines whether an unlicensed frequency band is available before using the unlicensed frequency band. Since communication systems of different operators and communication systems under different communication protocols have equal rights to use the unlicensed frequency band, a problem urgent to be solved in the industry is how to use transmission resources of the unlicensed frequency band fairly and effectively.